Urgent changes must be made to the way A&E units are run - or the system could collapse, doctors and managers say.
Both the College of Emergency Medicine and Foundation Trust Network have put forward proposals to overhaul the system.
Funding and staffing have been highlighted as key issues.
Health Secretary Jeremy Hunt said it was "very tough out there" and ministers would deal with it by "better joining up" health and social care.
The warnings come as fears grow over whether the NHS can continue to cope with rising demand.
Last week both ministers and the NHS regulator admitted the problems were a cause for concern.
A&E attendances have risen by 50% in a decade and this winter the NHS in England started missing its four-hour waiting time target.
Pressures have been noted in other parts of the UK too.
The review by the College of Emergency Medicine - based on feedback from more than half the A&E units in the UK - said the scale of the challenge was the biggest for a decade.
It said there were shortages in both middle-grade and senior doctors. As well as highlighting the workforce problem, the college also said more needed to be done to reduce unnecessary attendances.
It believes between 15% and 30% of patients do not need A&E care and instead could be treated in non-emergency settings.
Meanwhile, the Foundation Trust Network (FTN) highlighted the funding system in England which penalises A&E units seeing a rise in patients.
Under rules designed to encourage the system to reduce A&E admissions, hospitals are only paid 30% of the normal fee for an emergency admission when the numbers rise above the levels that were seen in 2008-9.
But with the NHS failing to curb the rise in patients, that is costing some hospitals millions of pounds a year.
FTN chief executive Chris Hopson said: "Unless we can change the funding structure, the A&E system is going to fall over. We simply cannot carry on."
He said the last winter was "very, very difficult" although with the weather now improving there were signs the system was stabilising.
But he added: "Unless we can make some really significant changes over the next six months I think it's pretty clear the system is in danger of falling over next winter."
NHS England has already agreed to plough some of the money it saves through these rules back into the system to support the most troubled A&E units in the short-term.
It has also ordered a review of emergency and urgent care, led by medical director Sir Bruce Keogh. The findings are expected to be published soon.
Shadow health secretary Andy Burnham said: "Warnings don't come any more serious than this.
"Too many hospitals around England are sailing dangerously close to the wind, operating way beyond safe bed occupancy levels."
He told BBC Radio 5 live the situation could be improved by "the full integration of health and social care - a national health and care service, if you like".
"As people get older, we've got to support them in their homes so they don't end up in hospital," he added.
"But we've also got to deal with the here and now and we can't have people waiting on trolleys in corridors and being treated in the back of ambulances.
"The government has got to get a grip on the situation and it's got to do it now."
Health Secretary Jeremy Hunt, meanwhile, told 5 live: "I've visited many, many A&E departments and staff are working extremely hard, you can see the lines on their eyes, people are very tired, they're obviously working hard, 24/7, and it's incredibly impressive what they're doing."
He said that, since the government came into power, the number of people using A&E had gone up by a million a year.
"There is that pressure and we have to do something about it," he said.
He admitted there was "a lack of joined-up thinking between health and social care system which we're sorting out".
He cited a care bill, set out in the Queen's Speech, which will introduce a cap on the cost of social care and give carers the legal right to support from their local council.
"That's also a very big problem because what you're finding in a typical hospital is maybe 100 beds are full of people who actually don't need to be in hospital but the doctors aren't able to discharge them into the social care system."
He said the government was putting £7.2bn into the social care system "to protect it against cuts".
Figures for week ending 7 April 2013, to reflect period of higher demand during colder weather.